49.6. 客户端上的异步处理

JAX-RS 2.0 支持在客户端一侧进行异步调用。支持两种不同的异步处理方式：使用 java.util.concurrent.Future<V&gt; 返回值；或通过注册调用回调。

使用 Future<V > 方法异步处理，您可以异步调用客户端请求，如下所示：

// Java
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.Client;
import java.util.concurrent.Future;
import javax.ws.rs.core.Response;
...
Client client = ClientBuilder.newClient();
Future<Response> futureResp = client.target("http://example.org/bookstore/books/123")
                     .request("application/xml")
                     .async()
                     .get();
...
// At a later time, check (and wait) for the response:
Response resp = futureResp.get();

您可以对输入的响应使用类似的方法。例如，若要获得类型为 BookInfo 的回答：

Client client = ClientBuilder.newClient();
Future<BookInfo> futureResp = client.target("http://example.org/bookstore/books/123")
                     .request("application/xml")
                     .async()
                     .get(BookInfo.class);
...
// At a later time, check (and wait) for the response:
BookInfo resp = futureResp.get();

您可以使用 Future<V> 对象访问返回值，而是定义调用回调（使用 javax.ws.rs.client.InvocationCallback<RESPONSE&gt;），如下所示：

// Java
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.Client;
import java.util.concurrent.Future;
import javax.ws.rs.core.Response;
import javax.ws.rs.client.InvocationCallback;
...
Client client = ClientBuilder.newClient();
Future<Response> futureResp = client.target("http://example.org/bookstore/books/123")
                     .request("application/xml")
                     .async()
                     .get(
    new InvocationCallback<Response>() {
        @Override
        public void completed(final Response resp) {
            // Do something when invocation is complete
            ...
        }

        @Override
        public void failed(final Throwable throwable) {
            throwable.printStackTrace();
        }
    });
...

您可以对输入的响应使用类似的方法：

// Java
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.Client;
import java.util.concurrent.Future;
import javax.ws.rs.core.Response;
import javax.ws.rs.client.InvocationCallback;
...
Client client = ClientBuilder.newClient();
Future<BookInfo> futureResp = client.target("http://example.org/bookstore/books/123")
                     .request("application/xml")
                     .async()
                     .get(
    new InvocationCallback<BookInfo>() {
        @Override
        public void completed(final BookInfo resp) {
            // Do something when invocation is complete
            ...
        }

        @Override
        public void failed(final Throwable throwable) {
            throwable.printStackTrace();
        }
    });
...